1. Field Of The Invention
This invention relates to valves used in downhole well tools, and more particularly, but not by way of limitation, to a circulating valve which may be used to allow circulation of fluid through a downhole tool as it is run into a well bore on a coiled tubing. The valve may also be used as a deflation valve for inflatable packers associated with a downhole tool.
2. Description Of The Prior Art
On various types of downhole tools, for example but not by way of limitation, inflatable packers, it is often desirable to circulate fluid in the well as the tool is being run into the well bore. A number of circulating valves have been developed in the past, but most of these require manipulation, including rotation, of the tool string. Such rotation is not possible on tools run into the well bore on coiled tubing.
The present invention solves this problem by allowing circulation of fluids as the tool is run into the well. The valve is closed simply by pumping fluid through the tool so that a differential pressure closes the valve without any manipulation of the tool string being necessary.
A particular problem when inflatable packers are run into a well bore is involved in deflating the packers. Such tools are preferably run into the well bore with a check valve in the tubing string so that fluid cannot flow back upwardly through the tubing. Unfortunately, this also can prevent venting of fluids from the packer. The valve of the present invention acts as a deflation valve which may be reopened during a deflation operation so that fluids from the packer may be vented through the valve into the well annulus, thereby allowing packer to deflate.